Non-woven fabrics are well-suited for applications which require a low cost fibrous web. Examples are disposable polishing or washing cloths.
Non-woven fabrics are normally produced from a web of loosely associated fibers that are subjected to a fiber rearranging method to entangle and mechanically interlock the fibers into a unitary reticular network. The fiber rearrangement is achieved under the effect of fluid forces applied to the fibers through a fluid permeable, web confining and supporting structure comprising a rigid apertured member with a predetermined pattern of fluid passages, and a flexible foraminous sheet disposed in a face-to-face relationship to the apertured member.
In one form of construction, the rigid apertured member is a rotating hollow drum and the flexible foraminous sheet is an endless screen belt in overlapping relationship with the hollow drum and advancing therewith. The web of loosely associated fibers which forms the starting material of the non-woven fabric production method is confined between the drum and the screen belt and is advanced through a fluid stream creating the entangling forces acting to entangle the fibers.
The so-called "Rosebud" non-woven fabric production method requires that the source of the fluid stream be located outside the hollow drum, the fluid particles impinging on the fibers through the screen belt. In operation, the fibers are drawn by the fluid mass flowing out of the apertured hollow drum, into the fluid passages thereof, and they are mechanically interlocked and entangled in protuberant packings which are interconnected by flat fiber bundles extending over the land areas of the drum. The resulting non-woven fabric has a three-dimensional structure presenting a knobby side containing the apexes of the fiber packings, and a flat and smoother side containing the base portions of the fiber packings and the interconnecting bundles.
In a variant of the Rosebud method, known as the "Keyback" method, the direction of the fluid stream is reversed, whereby the fluid particles reach the fibers by passing through the fluid passages on the drum. In contrast to the Rosebud method, the fibers are packed together on the land areas of the drum forming a network with clear holes arranged into a pattern corresponding to the pattern of fluid passages on the hollow drum.
Canadian patent 1,143,929 issued to Johnson & Johnson, U.S.A. on Apr. 5, 1983 discusses in detail a method for manufacturing a non-woven fabric by fluid entanglement and constitutes a reference of interest to the present subject.
For a wide range of applications, non-woven fabrics having superior resistance characteristics are required. To achieve this objective, it is known from the prior art to apply a binder substance to the non-woven fabric in order to consolidate the fibrous network. The binder substance, when cured, establishes bonds between adjacent fibers and prevents them to move one relatively to the other. Accordingly, the tenacity of the non-woven fabric increases by virtue of a reduction in inter-fiber displacement when destructive forces act on the non-woven fabric.
For enhancing the aesthetical appearance of a non-woven fabric, it is common practice to print the non-woven fabric with a decorative pattern. Typically, this operation is carried out at a printing station after the binder has been heat-cured. The printing station operates according to the principle of a common printing press. More specifically, it comprises a printing roll which is engraved to form a colorant transfer surface applying colorant, such as ink, according to a desired pattern on the surface of the non-woven fabric.
A drawback of traditional methods for manufacturing a non-woven fabric marked with a print, resides in the necessity to provide an additional drying station on the production line to dry the print before the non-woven fabric can be handled for further processing. Accordingly, the non-woven fabric is subjected in the overall to two successive drying operations, one for curing the binder and the other one for drying the print, which increase the complexity of the production equipment and the manufacturing cost of the final product.